In general, a certain graphic user interfaces (GUIs) are often present in electronic devices, and a virtual adjusting button is one of the GUIs. The virtual adjusting button is used for simulating real knob-operated control. However, since the exterior appearances of the electronic devices become slimmer and more compact, performing control on the electronic devices with the virtual adjusting button becomes troublesome. That is to say, due to the downsizing of the electronic devices, screens provided with the electronic devices are also scaled down. Therefore, the virtual adjusting button displayed on the screens also decreases. Accordingly, when a user intends to control the virtual adjusting button on a downsized screen to perform adjustment of a setting value such as the volume, a certain problems are bound to occur. For example, difficulty in identifying the scale count of the virtual adjusting button (such as a knob), and also difficulty in controlling a rotating degree of the knob with precision.
Even if under certain circumstances, a developer designs scale graduations for the knob so that simply clicking directly on a scale graduation with a mouse cursor adjusts the setting value represented by the scale graduation; however, such a practice still fails to solve the problem of difficulty in identifying the scale count, and adjustment cannot be performed with precision, which misses on the point of having the knob. In addition, under other circumstances, the developer arranges a slider for the virtual adjusting button, and the user controls the rotating degree of the knob by dragging the slider. Nonetheless, such a solution is still not intuitive during operation, and the precision also awaits improvement.